A conventional PCR method uses an external heater as a means for raising the temperature of a reaction solution for a PCR cycle, and heat of the heater is transmitted to the reaction solution via a wall of a reaction container to heat the reaction solution. However, in this case, the wall is first heated, and the reaction solution is heated by heat of the wall, and thus the response rate of temperature control is low, and heat is diffused along the wall to result in poor energy efficiency.
Therefore, it has been proposed to make electric current flow through a reaction solution to directly heat the reaction solution by Joule heat (refer to, for example, Non Patent Literature 1).